Quick update. I'm in Cincy and the temperature dropped about 30 degrees over the past day to about 35 degrees in the morning. The grinding is now really noticeable at nearly every turn, even at higher speeds. It seems to be a problem that gets worse over time (I now have about 700 miles on car) and with the weather. Called BMW Customer Service today to report the problem. I will let you know when I hear from them or the dealer.